The chief of the Criminal Division of the U.S. Attorney’s Office in Arizona is refusing to testify before Congress regarding Operation Fast and Furious, the federal gun-running scandal that sent U.S. weapons to Mexico.

Patrick J. Cunningham informed the House Oversight Committee late Thursday through his attorney that he will use the Fifth Amendment protection.

Cunningham was ordered Wednesday to appear before Chairman Darrell Issa and the House Oversight Committee regarding his role in the operation that sent more than 2,000 guns to the Sinaloa Cartel. Guns from the failed operation were found at the murder scene of Border Agent Brian Terry.